Comparison of double-acting and single-acting synthetic jets

This paper deals with an experimental comparison of double-acting synthetic jets (DASJs) with commonly used single-acting synthetic jets (SASJs). The DASJ is a fluid jet resulted from interactions of two pulsatile jets operating in anti-phase, i.e., a central round SASJ and an annular hybrid synthetic jet in coaxial arrangement. The experiments were performed by using water as the working fluid with actuation frequencies from 2 Hz to 12 Hz. The phase-locked measurements by means of particle image velocimetry (PIV) have shown the basic difference of the time-averaged flow-field and demonstrated the characteristic changes in a cycle of synthetic jet. The velocity and vorticity fields of DASJ and SASJ are compared. It shows that the former has in general higher vorticity (more than two times) and narrower jet width (only 43.7%) of the latter. A saddle point on the jet axis exists at the distance about one diameter of central nozzle of the actuator, i.e., the flow velocity is always positive for x/Dc > 1. In short, DASJ has revealed good potential with significant vorticity enhancement for the design of synthetic jet in heat transfer applications.